Here are 30 important interview questions about Spring JDBC Template, along with their answers:
1. What's the nature of Spring JDBC Template and Why is it utilized?
-An answer: Spring JDBC Template is a part of Spring Framework. It simplifies JDBC operations. Spring JDBC Template is used to avoid a lot of boilerplate code that is really meant for other database-related functions such as opening and closing of connections, handling exceptions, executing SQL queries, etc.
2. How is Spring JDBC Template configured in a Spring Boot application?
-Answer: One can configure Spring JDBC Template by adding relevant dependencies in pom.xml and defining a Datasource bean. Spring Boot will automatically configure JdbcTemplate once it finds a Datasource bean.
3. Describe the procedure to execute SQL query using Spring JDBC Template.
-Answer: The steps are DataSource set-up, JdbcTemplate instantiation, SQL query definition, and execution through methods like queryForObject, query, and update.
4. How does Spring JDBC Template make your life easier in Java when interacting with the database?
-Answer: Spring JDBC Template takes care of resource management and exception handling, which enables the developer to concentrate on writing SQL queries and mapping the resulting data to objects without doing the low-level JDBC API hassle.
5. What is a DataSource in Spring JDBC Template?
-Answer: DataSource is a factory for database connections. It is seen in JdbcTemplate, which acquires and manages database connections with the help of a DataSource.
6. How do I make a simple query using Spring JDBC Template?
-Answer: A simple query can be done via methods such as queryForObject, queryForList, or query, by passing the SQL along with the RowMapper to map a result set to an object.
7. How do you perform a simple query using Spring JDBC Template?
-Answer: The `query` method is for getting multiple rows from the database, while the `queryForObject` is for getting only a single result. `query` requires an additional argument, that is, a `RowMapper`, to map each row of the resultset.
8. How does one handle SQL exceptions in Spring JDBC Template?
- Answer: Spring JDBC Template translates SQL exceptions to `DataAccessException`, a runtime exception, so that it doesn't require explicit catch blocks for `SQLException`.
9. What is the role of the `RowMapper` in Spring JDBC Template?
- Answer: `RowMapper` is an interface that maps rows of a result set to Java objects and thus avoids the hassle of converting database rows to domain objects.
10. How can we perform batch updates using Spring JDBC Template?
- Answer: Batch updates can be done using the `batchUpdate` method of the `JdbcTemplate`. This method takes an array of SQL statements or a `BatchPreparedStatementSetter`.
11. Explain how you can work with named parameters in Spring JDBC Template.
- Answer: Named parameters tied up with `NamedParameterJdbcTemplate` allow developers to employ such type of named parameters rather than positional parameters for input in SQL query calls.
12. State the role of the `PreparedStatementCreator` and `PreparedStatementSetter` in Spring JDBC Template.
- Answer: `PreparedStatementCreator` creates a `PreparedStatement`, while `PreparedStatementSetter` is used to set actual parameter values in the `PreparedStatement`.
13. Insert operation using Spring JDBC Template.
Answer: Insert operation can be done by calling update method of JdbcTemplate providing SQL insert statement and required parameters.
14. How transactions are handled using Spring JDBC Template?
Answer: Transactions can be managed declaratively by using the annotation @Transactional or programmatically using DataSourceTransactionManager.
15. What is SimpleJdbcInsert in Spring JDBC Template?
Answer: SimpleJdbcInsert is a helper class which only concerns how to insert data into a table and does not require an explicit SQL statements.
16. Delete operation is performed by the help of Spring JDBC Template.
Answer: Delete operation by update method providing SQL delete statement along with required parameters.
17. What is the advantage of Spring JDBC Template from plain JDBC?
Answer: Automatic resource management, exception translation, and simplification of code by eliminating boilerplate code and providing higher-level API to perform operations on database.
18. Explain the steps for mapping the query results into a user-defined object in Spring JDBC Template.
Answer: You will have to implement RowMapper interface which will define how each row of the result set should be mapped to a user defined object and pass the RowMapper to the query method with the SQL query.
19. How can one perform the update operation using Spring JDBC Template?
- Answer: An update operation is done using the method update, providing the relevant parameters and the SQL update statement.
20. What does `JdbcTemplate` class do within Spring?
- Answer: The class `JdbcTemplate` has utility methods to simplify interaction with a relational database system while taking care of the resource management, exception translation, and the core of the tasks of executing SQL queries and update operations and retrieving their results.
21. How is a stored procedure executed using Spring JDBC Template?
- Answer: You can make use of SimpleJdbcCall class which provides a fluent API for calling stored procedures.
22. Describe the `ResultSetExtractor` interface and how it works in Spring JDBC Template.
- Answer: ResultSetExtractor is an interface designed for processing a complete ResultSet at once. It is used when you wish to implement a custom result extraction logic from that ResultSet.
23. How does Spring JDBC Template handle pagination?
- Answer: Result sets can be paginated by using the LIMIT tag in the SQL query to restrict the included records and offset the cursor using the OFFSET tag. The paginated result can be obtained by executing the query using the query method.
24. What is the purpose of NamedParameterJdbcTemplate in Spring?
- Answer: Support for named parameters allows the SQL query to be far more readable and maintainable as compared to positional parameters because it is not dependent on the sequence of parameters.
25. How would you implement logging SQL statements executed with Spring JDBC Template?
- Answer: Log SQL Statements using log settings for `org.springframework.jdbc` in your logging framework (Logback, Log4j, etc).
26. Explain the usage of JdbcCall in Spring JDBC Template.
- Answer: JdbcCall can be used for calling stored procedures and functions. It has a fluent API to provide procedure name, parameters most importantly result extraction.
27. How do you use the `MapSqlParameterSource` class in Spring JDBC Template?
- Answer: MapSqlParameterSource is a means of providing named parameters and their values for SQL queries and is generally used in context with NamedParameterJdbcTemplate.
28. Discuss some of the limitations of Spring JDBC Template.
- Answer: Spring JDBC Template abstracts away much of the boilerplate code for you, but it does not really cater to ORM functionality. This means that it is limited to JDBC and, in most cases, will need to be developed for handling complex object-relational mappings.
29. How would you get Spring JDBC Template to handle very large results sets with ease?
- Answer: Very large result sets may be handled by using a `ResultSetExtractor` or `RowCallbackHandler` to iterate through the rows successively and avoid loading the entire ResultSet into memory.
30. Explain how to use custom error handling with Spring JDBC Template.
- Answer: You can use custom error handling if you catch the DataAccessException, and then define your custom exception translation or handling logic in your application.
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